Seven-week persistence of an oviposition-deterrent pheromone.

Cabbage leaves sprayed with a water solution of the oviposition-deterrent pheromone ofPieris brassicae remain deterrent to ovipositing females for at least 14 days. Under laboratory conditions, the pheromone, when dried on a glass surface, retains activity for a period of at least 7 weeks. After 7 days under vacuum conditions, some pheromone is still present, indicating a low volatility and / or high stability of (an active fraction of) the pheromone. After 125 eggs are slowly rinsed with 300 ml water, they still release detectable quantities of the pheromone.